Variable nozzle two-dimensional / three-dimensional parametric modeling method

Abstract

The invention provides a two-dimensional / three-dimensional parametric modeling method for a variable nozzle. The method comprises the following steps: S1, defining reference blade profile parameters of the variable nozzle; s2, adjusting the position of a control point on the meridian flow channel according to the reference blade; s3, determining a two-dimensional mean camber line in combination with basic parameters of the nozzle blade; s4, carrying out inverse problem solving on the blade profile parameters; s5, designing a two-dimensional blade profile based on an NURB curve; s6, a bent blade profile is obtained based on the stacking line of the blade; s7, a twisted blade profile is obtained based on the blade twisting angle; and S8, the two-dimensional blade profiles are subjected to three-dimensional stacking in the radial direction, and the final three-dimensional blade profile geometrical shape is generated. According to the two-dimensional / three-dimensional parametric modeling method for the variable nozzle, a'mean camber line + multi-parameter method 'is adopted for the structure of the nozzle blade, the turbine flow can be better controlled, and the requirement for flow adjustment is met.

Description

Technical Field

[0001] The present invention belongs to the field of turbocharger structures, and in particular relates to a variable nozzle two-dimensional / three-dimensional parametric modeling method. Background Art

[0002] With the rapid development of technologies in fields such as aerospace, power machinery, and fluid mechanics, variable nozzle technology has been widely applied in many important fields such as engines, jets, and rockets. By adjusting the geometric shape of the nozzle, the variable nozzle can optimize the fluid injection efficiency under different working conditions, improve the performance of the engine, reduce noise, and increase thrust. Therefore, designing and manufacturing an efficient and precise variable nozzle has become an important task in modern engineering. The design goal of the radial turbine variable nozzle is to optimize the air flow direction, velocity, and pressure by adjusting the nozzle blade angle, thereby improving the efficiency and overall performance of the turbine. For a radial turbine, the role of the nozzle blade is to adjust the air flow entering the turbine and ensure the best flow direction and flow rate at the turbine inlet, so as to adapt to different working conditions. Therefore, to meet the design requirements of a wide flow rate and high efficiency of the supercharger, based on the structure and actual working condition design characteristics of the variable nozzle, it is necessary to study a two-dimensional / three-dimensional modeling method for high-precision and high-efficiency variable nozzles, realize a precise parametric design method, and meet the best airfoil design scheme for specific working conditions and performance requirements. Summary of the Invention

[0003] In view of this, the present invention aims to propose a variable nozzle two-dimensional / three-dimensional parametric modeling method, which not only realizes the adjustment requirement of the turbine flow rate, but also has high calculation accuracy and fast calculation speed, meets the application requirements of diesel engines, improves the level of rapid generation and optimization design of key components of the turbocharger, and improves work efficiency.

[0004] To achieve the above object, the technical solution of the present invention is realized as follows:

[0005] A variable nozzle two-dimensional / three-dimensional parametric modeling method includes the following steps:

[0006] S1: Define the reference airfoil parameters of the variable nozzle;

[0007] S2: Adjust the positions of the control points on the meridional flow path according to the reference blades;

[0008] S3: Define the two-dimensional mean camber line in combination with the basic parameters of the nozzle blade;

[0009] S4: Solve the inverse problem of the airfoil parameters;

[0010] S5: Design a two-dimensional airfoil line based on NURB curves;

[0011] S6: Obtain a cambered airfoil based on the stacking line of the blade;

[0012] S7: Obtain a twisted airfoil based on the blade twist angle;

[0013] S8: Stack the 2D airfoil radially to generate the final 3D airfoil geometry.

[0014] Furthermore, the method for determining the 2D mean camber line by combining the basic parameters of the nozzle blade in S3 is as follows:

[0015] Before designing the mean camber line of the airfoil, the basic parameters of the nozzle blade should be determined according to the Euler turbine equation in combination with the operating condition parameters, including the inlet air flow angle a1 of the blade, the outlet air flow angle a2 of the blade, the installation angle α of the nozzle blade y , and the chord length l of the blade; Establish a coordinate system by taking the airfoil of a common blade. Since the leading edge of the inlet or the trailing edge of the outlet of the common nozzle blade airfoil is a circle, the mean camber line of the airfoil starts from the center of the inlet circle and ends at the center of the outlet circle;

[0016] Regarding the mean camber line itself as a streamline in the flow field, the streamline must have continuous third-order derivatives. Therefore, the equation of the mean camber line is set as a fourth-degree polynomial equation, that is:

[0017] y = (x) = a0 + a1x + a2x 2 + a3x 3 ;

[0018] In the formula: a0, a1, a2, and a3 are the equation coefficients, dimensionless.

[0019] The coordinates of the center O i of the inlet circle of the airfoil where the calculated mean camber line is located are:

[0020] x i = 0, = t / 2;

[0021] In the formula: t is the blade pitch;

[0022] The coordinates of the center O o of the outlet circle of the airfoil where the mean camber line is located are: x0 = s, y0 = t / 2 + l·sin(α y );

[0023] In the formula: l is the chord length of the blade, and α y is the rotor airfoil angle;

[0024] From the flow process of the air in the turbine blade and the definition of the inlet liquid flow angle, it can be known that at the center of the inlet circle of the mean camber line, its tangent is consistent with the streamline direction of the air entering the blade. Therefore, the slope of the mean camber line at its starting point is:

[0025] y = a1 + 2a2x i + 3a3xi = tan(α1);

[0026] Where: α1 is the inlet angle of the rotor blade profile;

[0027] Similarly, at the center of the outlet circle of the mean camber line, the tangent line is in the same direction as the streamline of the fluid flowing out of the blade. Therefore, the slope of the mean camber line at its end point is:

[0028] y0' = a1 + 2a2x0 + 3a3x0 2 = tan(α2);

[0029] Where: α2 is the outlet angle of the rotor blade profile; According to the above 4 known conditions, a system of linear equations can be obtained:

[0030]

[0031] By solving this system of linear equations, the equation of the mean camber line can be obtained.

[0032] Furthermore, the method for solving the inverse problem of blade profile parameters in S4 is as follows:

[0033] In the algorithm for fitting discrete points with NURB curves, when calculating the distance from a certain discrete point to the curve, the golden section algorithm is adopted, and the number of iterations for calculating the weight of each curve segment is controlled within 30 - 40 times.

[0034] Furthermore, the method for the two-dimensional blade profile line based on NURB curves in S5 is as follows:

[0035] The mathematical description of the NURB curve is:

[0036]

[0037] where, p i is the control point position vector, B i,n (t) is the Bernstein basis function, and Wi is the weight of the i-th control point.

[0038] Compared with the prior art, the variable nozzle two-dimensional / three-dimensional parametric modeling method of the present invention has the following advantages:

[0039] (1) For the variable nozzle two-dimensional / three-dimensional parametric modeling method of the present invention, the structural design of the nozzle blade adopts the "mean camber line + multi-parameter method" for design, which can better control the turbine flow rate and meet the needs of flow regulation.

[0040] (2) For the variable nozzle two-dimensional / three-dimensional parametric modeling method of the present invention, the blade profile is designed with bending and torsion, which improves the design accuracy and application level, and realizes the fine control of the turbine flow rate. Description of the Drawings

[0041] The accompanying drawings, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0042] Figure 1 It is a flowchart of the variable nozzle two-dimensional / three-dimensional parametric modeling method described in the embodiments of the present invention;

[0043] Figure 2 It is a schematic diagram of the control point positions on the meridional flow channel described in the embodiments of the present invention;

[0044] Figure 3 It is a schematic diagram of the blade profile coordinate system described in the embodiments of the present invention;

[0045] Figure 4 It is a flowchart of solving the inverse problem of blade profile parameters described in the embodiments of the present invention;

[0046] Figure 5 It is a schematic diagram of a two-dimensional blade profile line based on NURB curves described in the embodiments of the present invention;

[0047] Figure 6 It is a schematic diagram of a curved blade profile described in the embodiments of the present invention;

[0048] Figure 7 It is a schematic diagram of a twisted blade profile described in the embodiments of the present invention;

[0049] Figure 8 It is a schematic diagram of the three-dimensional blade profile geometry described in the embodiments of the present invention;

[0050] Figure 9 It is the reference blade profile described in the embodiments of the present invention;

[0051] Figure 10 It is a schematic diagram of inverse problem fitting described in the embodiments of the present invention;

[0052] Figure 11 It is a schematic diagram of two-dimensional nozzle parametric design after setting nozzle parameters described in the embodiments of the present invention;

[0053] Figure 12 It is a schematic diagram of the stacking line after blade bending described in the embodiments of the present invention;

[0054] Figure 13 It is a design schematic diagram after blade twisting described in the embodiments of the present invention;

[0055] Figure 14 It is a schematic diagram of the three-dimensional model of the nozzle blade described in the embodiments of the present invention. Detailed implementation manners

[0056] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0057] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0058] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0059] The present invention will be described in detail below with reference to the drawings and in combination with embodiments.

[0060] A variable nozzle two-dimensional / three-dimensional parametric modeling method, as Figures 1 to 14 shown, includes the following steps:

[0061] S1: To meet the turbine flow regulation requirements, clarify the reference blade profile parameters of the variable nozzle;

[0062] S2: According to the reference blade, adjust the positions of the control points on the meridional flow path (see Figure 2 );

[0063] Based on the meridional flow path information in the design requirements as the meridional flow path of the designed blade profile, this is also convenient for optimization on the basis of the reference blade. By adjusting the positions of the control points on the meridional flow path, precise control of the expansion and contraction of the flow path can be achieved, and the geometric shape of the flow channel can be optimized to meet the aerodynamic and structural requirements under different working conditions.

[0064] S3: Combine the basic parameters of the nozzle blade to clarify the two-dimensional mean camber line design;

[0065] Before designing the mean camber line of the blade profile, the basic parameters of the nozzle blade should be determined according to the Euler turbine equation in combination with the operating conditions parameters, including the inlet and outlet angles (the inlet air flow angle a1 of the blade, the outlet air flow angle a2 of the blade), the nozzle blade installation angle α y , the chord length l of the blade, etc. Take the blade profile of common blades (see Figure 3 ) to establish a coordinate system. Since the inlet leading edge or the outlet trailing edge of the common nozzle blade profile is a circle, the mean camber line of the blade profile starts from the center of the inlet circle and ends at the center of the outlet circle.

[0066] The mean camber line itself can be regarded as a streamline in the flow field. The streamline must have continuous third-order derivatives, so the mean camber line equation can be set as a fourth-degree polynomial equation, that is:

[0067] y = (x) = a0 + a1x + a2x 2 + a3x 3 ;

[0068] In the formula: a0, a1, a2, a3 are the equation coefficients, dimensionless.

[0069] The coordinates of the center O i of the mean camber line at the inlet circle of the blade profile are:

[0070] x i = 0, = t / 2;

[0071] In the formula: t is the blade pitch.

[0072] The coordinates of the center O o of the mean camber line at the outlet circle of the blade profile are: x0 = s, y0 = t / 2 + l·sin(α y );

[0073] In the formula: l is the chord length of the blade, α y is the rotor blade profile angle.

[0074] From the flow process of the air flow in the turbine blade and the definition of the inlet liquid flow angle, it can be known that at the center of the inlet circle of the mean camber line (the starting point of the mean camber line), the tangent line is consistent with the streamline direction of the air flow entering the blade. Therefore, the slope of the mean camber line at its starting point is:

[0075] y = a1 + 2a2x i + 3a3x i = tan(α1);

[0076] In the formula: α1 is the inlet angle of the rotor blade profile.

[0077] Similarly, at the center of the outlet circle of the mean camber line (the ending point of the mean camber line), the tangent line is consistent with the streamline direction of the liquid flow flowing out of the blade. Therefore, the slope of the mean camber line at its ending point is:

[0078] y0′ = a1 + 2a2x0 + 3a3x0 2 = tan(α2);

[0079] Where: α2 is the outlet angle of the rotor blade profile. Based on the above 4 known conditions, a linear equation system can be obtained:

[0080]

[0081] By solving this linear equation system, the mean camber line equation can be obtained. The mean camber line design is strictly derived based on the blade profile geometric conditions and flow parameters, without involving empirical parameters. Therefore, the mean camber line designed according to this method can better meet the actual flow conditions.

[0082] S4: Solve the inverse problem of blade profile parameters;

[0083] To obtain the parameters and control points of the reference blade, it is necessary to solve the inverse problem of the reference blade, that is, to obtain the blade profile parameters based on the discrete points of the blade shape. When solving the inverse problem of this parameterization method, it should be ensured that the parameterized blade shape is as close as possible to the original data points and the error is as small as possible. It should also be ensured that when the number and relative density of the original data points change significantly, the parameterized results will not change significantly. On the premise of ensuring the above requirements, the calculation speed should be improved as much as possible.

[0084] In this process, a two-layer nested golden section optimization algorithm is used to solve the maximum thickness point, which has high calculation accuracy and fast calculation speed.

[0085] The quality of the inverse problem solution results depends crucially on the algorithm when fitting discrete points with NURB curves. Among them, when calculating the distance from a certain discrete point to the curve, a golden section algorithm is used. Due to multiple loop nesting, the calculation speed is slow. It is recommended to control the number of iteration times for calculating the weight of each curve segment within 30 - 40 times. For the specific process, see Figure 4 .

[0086] S5: Design a two-dimensional blade profile line based on NURB curves;

[0087] NURB curve, that is, Non-Uniform Rational Bezier curve. The ordinary Bezier curve controls the curve shape through the positions of control points. Its mathematical description is:

[0088]

[0089] where, p i is the control point position vector, and B i,n (t) is the Bernstein basis function:

[0090]

[0091] Compared with the Bezier curve, the characteristic of the NURB curve is that each control point has a weight. The NURB curve can control the curve shape not only through the positions of the control points but also by changing the weights of the control points: the greater the weight of a certain control point, the closer the curve is to this control point; when the weight of a certain control point is 0, the control point has no control effect on the curve; when the weights of all control points are 1, the NURB curve degenerates into a Bezier curve. The mathematical description of the NURB curve is as follows:

[0092]

[0093] where p i is the control point position vector, B i,n (t) is the Bernstein basis function, W i is the weight of the i-th control point. See the schematic diagram in Figure 5 .

[0094] S6: Obtain the cambered airfoil based on the stacking line of the blade (see Figure 6 );

[0095] S7: Obtain the twisted airfoil based on the blade twist angle (see Figure 7 );

[0096] S8: Stack the two-dimensional airfoil radially to generate the final three-dimensional airfoil geometry (see Figure 8 ).

[0097] The specific embodiments are as follows:

[0098] 1) To meet the design accuracy and working condition requirements, first design the reference airfoil (see Figure 9 ). According to the reference blade, adjust the positions of the control points on the meridional flow path, and inversely solve the parameters of the airfoil shape based on the discrete points of the airfoil shape, that is, inverse problem fitting (see Figure 10 );

[0099] 2) Input the basic parameters of the nozzle blade and design the two-dimensional airfoil line based on the NURB curve. The specific parameters are: inlet air flow angle -10°, outlet air flow angle 5°, front wedge angle 45°, rear wedge angle 10°, chord length 15 mm, maximum thickness (radius) 1 mm, non-dimensional axial position of the maximum thickness 0.3, leading edge radius 0.5 mm, trailing edge radius 0.2 mm, nozzle blade rotation angle 45°, turbine radius 35 mm, thus forming the two-dimensional nozzle parametric design (see Figure 11 ).

[0100] 3) Define the blade camber parameters as: root camber angle 20°, root camber height 0.3 mm, tip camber angle 0°, tip camber height 0 mm, and obtain the cambered airfoil based on the stacking line of the bladeFigure 12 );

[0101] 4) The blade twist parameters are specified as: root twist angle -10°, middle twist angle 0°, top twist angle 10°. Based on the blade twist angle, the twisted blade profile is obtained (see Figure 13 ), and finally the three-dimensional model of the nozzle blade is formed (see Figure 14 ).

[0102] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A variable nozzle two-dimensional / three-dimensional parametric modeling method, characterized in that: It includes the following steps: S1: Define the reference blade profile parameters of the variable nozzle; S2: Adjust the positions of the control points on the meridional flow path according to the reference blades; S3: Define the 2D mean camber line in combination with the basic parameters of the nozzle blades; S4: Solve the inverse problem of the blade profile parameters; S5: Design a 2D blade profile line based on NURB curves; S6: Obtain the cambered blade profile based on the stacking line of the blades; S7: Obtain the twisted blade profile based on the blade twist angle; S8: Stack the 2D blade profile radially in three dimensions to generate the final three-dimensional blade profile geometry.

2. A variable nozzle two-dimensional / three-dimensional parametric modeling method according to claim 1, characterized in that: The method for defining the 2D mean camber line in S3 in combination with the basic parameters of the nozzle blades is as follows: Before designing the mean camber line of the blade profile, the basic parameters of the nozzle blade should be determined according to the Euler turbine equation in combination with the operating conditions parameters, including the inlet airflow angle a1 of the blade, the outlet airflow angle a2 of the blade, the installation angle α of the nozzle blade y and the chord length l of the blade; establish a coordinate system by taking the blade profile of common blades. Since the leading edge of the inlet or the trailing edge of the outlet of the common nozzle blade profile is a circle, the mean camber line of the blade profile starts from the center of the inlet circle and ends at the center of the outlet circle; The mean camber line itself is regarded as a streamline in the flow field. The streamline must have continuous third-order derivatives. Therefore, the mean camber line equation is set as a fourth-degree polynomial equation, that is: y = (x) = a0 + a1x + a2x 2 + a3x 3 ; In the formula: a0, a1, a2, a3 are the equation coefficients, dimensionless; The coordinates of the center O of the calculated mean camber line at the inlet circle of the blade profile are: i are: x i = 0, = t / 2; In the formula: t is the blade pitch; The center O of the middle arc at the outlet circle of the blade profile o has the coordinates: x0 = s, y0 = t / 2 + l·sin(α y ); Where: l is the blade chord length, α y is the rotor blade profile angle; From the flow-around process of the air flow in the turbine blade and the definition of the inlet liquid flow angle, it can be known that at the center of the inlet circle of the mean camber line, its tangent is consistent with the streamline direction of the air flow entering the blade. Therefore, the slope of the mean camber line at its starting point is: y = a1 + 2a2x i + 3a3x i = tan(α1); In the formula: α1 is the inlet angle of the rotor blade profile; Similarly, at the center of the outlet circle of the mean camber line, its tangent is consistent with the streamline direction of the liquid flow flowing out of the blade. Therefore, the slope of the mean camber line at its end point is: y0' = a1 + 2a2x0 + 3a3x0 2 = tan(α2); In the formula: α2 is the outlet angle of the rotor blade profile; According to the above four known conditions, a linear equation system can be obtained: By solving this linear equation system, the mean camber line equation can be obtained.

3. A variable nozzle two-dimensional / three-dimensional parametric modeling method according to claim 1, characterized in that: The method for solving the inverse problem of the blade profile parameters in S4 is as follows: In the algorithm for fitting discrete points by NURB curves, when calculating the distance from a certain discrete point to the curve, the golden section algorithm is adopted, and the number of iterations for calculating the weight of each curve segment is controlled within 30 - 40 times.

4. A variable nozzle two-dimensional / three-dimensional parametric modeling method according to claim 1, characterized in that: The method for the 2D blade profile line based on NURB curves in S5 is as follows: [[ID= where p i is the control point position vector, B i,n (t) is the Bernstein basis function, w i is the weight of the i-th control point.

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